Field of the Invention
The present invention relates to a plastics material liquid meter body, in particular a plastics material water meter body.
To be more precise, the present invention relates to a liquid meter body suitable for either of the two main types of fluid meter familiar to the person skilled in the art, namely volumetric meters, such as oscillating piston, diaphragm or nutating disk liquid meters, and velocity meters, such as turbine liquid meters (single-jet or multiple-jet) or screw liquid meters.
In the field of water meters, the meter body has for many years been made from a metal alloy such as brass. This material has good resistance to aging, and in particular the metrological performance of the meter and its water tightness are maintained over time.
For many years water meter manufacturers have been attempting to replace brass with plastics materials. A plastics material water meter body has many advantages, such as the possibility of modifying the design of the meter body to integrate new functions, a much wider range of colors than with brass, a significant saving in weight, a saving in manufacturing cost, a reduction in the noise generated by the meter in operation, and finally elimination of problems associated with the pollution of drinking water in contact with brass. However, there remains a major problem with plastics material water meter bodies in that they do not offer good mechanical performance, which leads in particular to problems with withstanding the high fluid pressure and with aging. For example, cracks have been observed to appear, leading to leaks, after a much shorter time period than the normal service life expected of a water meter.
An objective of the present invention is to alleviate the drawbacks previously cited by proposing a liquid meter body having improved mechanical performance. The liquid meter body in accordance with the invention includes a plastic material bucket which includes a lower portion delimited by a bottom and by a lower side wall and a cylindrical upper portion delimited by an upper side wall, said upper side wall joining onto the lower side wall at a shoulder, the lower portion defining a measuring chamber, said meter body further comprises entry and exit tubes having an external screwthread, said tubes each opening into the measuring chamber via a bore formed in the lower side wall and respectively forming an injector and an ejector, said meter body is characterized in that the bottom is elliptical.
The above type of water meter body significantly reduces the concentration of stresses. This prevents cracks appearing over time in the body of the meter, thereby preventing leaks.
In one embodiment at least one of the bores forming the injector and the ejector is elliptical.
In another embodiment each tube has a cylindrical exterior shape and at least one of the tubes has an elliptical interior shape.
The above type of tube shifts the concentrations of stresses outside the fragile areas of the part, in particular outside the weld lines between the tubes and the lower part of the bucket. Once again, the risk of cracks appearing at the level of the junction between the tubes and the lower portion of the bucket is considerably reduced.
A water meter equipped with a plastics material meter body having the above features has a much higher critical mechanical strength threshold than prior art plastics material meter bodies and reduces the level of mechanical stress for a given liquid pressure. Moreover, the above kind of meter body is found to have a service life much greater than prior art plastics material meter bodies. It must also be noted that the particular shape of the meter body, the bore and the tubes has no significant influence on the flow of the fluid in the meter body and does not influence the quality of flowrate measurement.